Zombie Edition is a mod based on original half-life concept, but you will play as a headcrab and, what is more interesting, as a zombie. Zombies can mutate to change their characteristics into three types and every type will have at least six upgrades including new weapons and abilities.
For further information please check this mod's Official Page.

Firstly, about trailer. Good news, our team had actually found our own videomaker. So, now you will get new trailers without me being busy about making them. His first work for my mod - this trailer about Rusher. I think, it is just from "must see" category.